大型转子—基础—土壤系统的动力分析

本文对大型汽轮发电机组-基础-土壤系统采用模态综合技术进行了动力分析.用弹性半空间理论建立土壤的模型,基础底板则通过弹性薄板的李兹(Ritz)函数近似解的形式来描述.用三维梁单元来建立基础底板以上的框架结构和转子系统的运动方程.此外,还用模态应变能的相对大小,在这种复杂机械结构系统存在的众多固有频率中,区分出哪些是属于主要为转子系统的固有频率,称为“重要振动固有频率”,以确定系统的临界转速.最后,对引进的一台500MW汽轮发电机组的动力特性进行了分析.     

汽轮机转子在气流力和油膜力作用下的非线性动力学特性

为了分析转子在油膜力和气流激振力共同作用下的非线性振动特性，本文以短轴承支撑的不平衡刚性对称Jeffcott转子系统为研究对象，首先分析转子在非稳态油膜力作用下的振动特性，然后分析转子在油膜力和气流激振力共同作用下的非线性振动特性。采用数值模拟的方法研究了系统的分岔和混沌特性，计算结果表明，考虑气流激振力和油膜力共同作用下的转子系统与仅考虑油膜力的转子系统相比，在相对进气速度v=30m／s时，随着无量纲转速ω的增加。二者都出现了周期运动和混沌运动多次交替出现的复杂运动特性，但是前者首次出现倍周期分岔和混沌运动时的转运提前，在定转速情况下，随着v的增大，系统最终在经历周期运动之后进入混沌运动，而且圆盘中心的最大振幅随着v的增大而增大。     

An engineering approach to blade designs for low to medium pressure rise rotor-only axial fans

Low to medium pressure rise axial fan equipment of the arbitrary vortex flow rotor-only type is widely used in industrial and commercial applications, with many of the installations and rotor designs being far from optimum. Complex computational methods exist for analyzing flows in, for example, high-speed axial flow compressors with multistage blade rows; however, the designers and manufacturers of low-speed, general-purpose axial flow fan equipment have been reluctant to embrace this technology. A simpler yet reliable design technique is presented that allows this category of ducted axial fan rotors, in the presence of swirl-free inlet flow, to be designed to achieve a specified duty with sufficient accuracy for engineering purposes. Practical blade design recommendations and limits, similar to those that exist for free vortex flow axial rotors, have been established for the arbitrary vortex flow rotor-only case.

The technique employs a straightforward engineering approach to arbitrary vortex flow axial fan rotor design, and the equation set can be solved by using relatively simple numerical methods. Estimates of pressure rise and shaft power characteristics for a proposed fan/rotor design can be computed and the design loop iterated until an acceptable set of blade parameters is identified. It is also possible to analyze the performance of an existing axial fan installation as a prelude to the design of a more efficient and effective replacement rotor.

Experimental data used in validating the design and analysis techniques are also presented. These data include comprehensive Cobra pressure probe surveys of local flow parameters downstream of three different low boss ratio, low solidity, arbitrary vortex flow rotors (all with circular arc camber line type blades) as well as fan performance characteristics for one of the experimental rotors configured as a direct-exhaust fan unit. Installation-dependent factors such as direct-exhaust losses and tip clearance effects are also examined. The analytical technique is shown to provide acceptable estimates of fan/rotor pressure rise performance and shaft power characteristics over a moderately wide range of blade angles and operating conditions.     

充水式潜水电机转子系统水摩擦力的数值分析

充水式潜水电机转子与轴向冷却水发生剧烈摩擦而产生的水摩擦力影响着转子系统的动力学特性。以850QS—3200型充水式潜水电机为研究对象,构建了电机转子与定子之间轴向冷却水的流场三维模型,运用标准k-ε湍流模型与SIMPLEC算法,基于computational fluid dynamics(CFD)软件平台依次数值模拟了转子外圆表面粗糙度、转子转速以及轴向冷却水流速等三者与转子外圆水摩擦力的作用机理与影响程度。结果表明转子系统水摩擦力随转子外圆表面粗糙度、转子转速以及轴向冷却水流速的增加而增加,可通过降低转子转速、提高转子表面粗糙度以及降低轴向冷却水速度等方法,降低充水式潜水电机转子水摩擦力以及由此产生的水摩擦损耗。     

恶劣环境下无人机双旋翼故障的智能监测系统设计

当前无人机双旋翼故障检测系统在恶劣环境下的抗干扰性能差,无法正常运行。设计一种小型、智能的适用于恶劣环境下的无人机双旋翼故障监测系统。首先规划了系统的总体结构,将便携式工控机作为系统运行的核心,用于对故障进行检测、提取故障数据进行存储和分析。然后利用数据采集模块对恶劣环境下无人机双旋翼相关数据进行采集,通过RS485总线完成主机和被监测无人机之间的数据传输。利用信号测试卡模块对数据采集模块接收的数据进行逻辑测试和故障诊断。最后采用无人机双旋翼故障检测算法对故障进行检测。实验表明,所设计系统具有较高的监测效率和精度,诊断效果良好。     

流道缩扩比对1+1/2对转涡轮高压动叶性能影响的研究

本文以1+1/2对转涡轮为背景,采用理论分析与数值模拟相结合的方法对某1+1/2对转涡轮高压动叶进行了优化设计.研究结果表明,流道缩扩比对高出口马赫数涡轮叶栅性能有重要影响,合理的流道缩扩比能减弱甚至消除尾缘内伸波,从而提升叶栅的性能.文中综合考虑了叶栅流道周向以及径向两个方向的扩张因素后选择了叶栅流道缩扩比,进行1+...     

Radial Yarn Movement in Yarn Duct of Interlacer

In order to find the relations between the production performonce of interlacer and its cross-sectional Shapcs of yarn duct,radial yarnsd movement in varions yarn ducts of interlacer and its effect on performance of interlaced yarn were studied in this paper. Seven interlacers,which were diffcrent in the cross- sectional shape of yarn duct,were made. Yarn motion in yarn duct of interlace was observed with optical fibers and photo- sensors. Performance of the interlaced yarn was evaluated by the number and the strength of tangles. Experfmental results disclose the relations between the yarn motions and the properties of the interlaced yarn. The interlacer with round yarn duct is capable of producing an interlaced yarn with bigger number of tangles,since It can make yarn transverse frequently the axis of air jet issuing from air jet nozzle. The interlacer with cornered shape of yarn duct makes yarn subjected to the action of compressed air for a longer time,which results in larger strength of tangles.     

Study on Wet Permeability Models of Yarns and Knitted Fabrics

Water transport through the pore structure of the knitted fabric can occur only in place where the fiber-water surface attraction force is greater than the water weight in the capillary. To investigate wet permeability of the knitted yarn in the fabric, a liquid transport model is established. The main factors which have significant influences on the liquid transport have been analyzed. It is derived from the argument that the optimal design for the knitted fabric with quick sweat transport property can be obtained.     

利用回归分析对正交试验结果进行修正

本文以纱线上浆率工艺参数正交试验为实例 ,利用回归分析的方法加以验证和修正 ,使工艺参数更符合实际情况 ,说明两种方法有较好的互补性 .     

Application of Volterra and Wiener Theories for Nonlinear Parameter Estimation in a Rotor-Bearing System

Volterra and Wiener theories provide the concepts of linear,bilinear, tri-linear, etc., kernels, which upon convolution with theexcitation force, can be employed to represent the response of anonlinear system. Based on these theories, higher-order frequencyresponse functions (FRFs) are employed to estimate the nonlinearstiffness of rolling element bearings, supporting a rigid rotor. Therotor-bearing assembly is idealized as a single-degree-freedom system,with cubic nonlinearity. The analysis involves a third-order kernelrepresentation of the system response. The first and third-order kerneltransforms are extracted from the measurements of the appliedwhite-noise excitation and the resultant response. A third-order kernelfactor is synthesized from this first-order kernel and is processedalong with the third-order kernel for estimation of the nonlinearparameter. Damping is assumed to be linear in the analysis. Theprocedure is demonstrated through measurements on a laboratory test rig.